Landing gear with dirigible landing wheel



LANDING GEAR WITH DIRIGIBLE LANDING WHEEL Filed April 17, 1940 4 Sheets-Sheet l I V e-3,.

HTTORHGYS June 4, 1945. P. E. MERCIER 2,401,364

LANDING GEAR WITH DIRlIGIBLE LANDING WHEEL v Filed April 17, 1940 4 Sheets-Sheet 2 INVEHTOR PIERRE ERNEST MERCER BY-' /wmfi, mi? a nrronusvs June 4, 3946.

P. E. MERCIER LANDING GEAR WITH DIRIGIBLE LANDING WHEEL 4 sheets-sheet :5

Filed April 17, 1940 P. E MERCIER LANDING GEAR WITH DIRIGIBLE LANDING WHEEL June 4, 1946.

Filed April 17, 1940 I I J/I/l/I/fl/l 4 Sheets-Sheet 4 Patented June 4, 1946 LANDING GEAR WITH DIRIGIBLE LANDING WHEEL Pierre Ernest Mercier, Neuilly-su'r-Seine, France; I vested in the Alien Property Custodian Application April 17, 1940, Serial No. 330,007 In France April 25, 1939 This invention relates to improvements in airplane landing gears having steerable landing wheels, and more particularly to a steerable land ing gear wherein the power for steering the landing wheel is derived from the rotation thereof.

Airplane landing gears having a steerable landing wheel, and more particularly those of the three-wheeled or tricycle type, possess a number of advantages. Included among these is the greater ease with which the plane may be maneuvered n the .ground.

It is generally necessary, however, especially in the case of medium and heavily loaded airplanes, to employ a servo-motor for directing the steerable landing wheel. Heretofore compressed air or a liquid under pressure has been employed to feed such servo-motors and the source of the power, that is, the supply of the compressed air or liquid, under pressure, has been located in the fuselage or wing structure of the airplane and has been recharged or maintained by energy derived from the motors.

It is an object of the present invention to provide, in association with an airplane landing gear, servo meansderiving its energy from the rotation of one or more of the landing wheels and transmitting power as required and under control of the pilot at all times to a steerable wheel forming a part of the landing gear assembly.

It is a further object of the invention to provide a servo means powered in the manner above described and associated in a landing gear assembly with means for damping or minimizing sidewise oscillation or shimmy of the landing wheels when the airplane is driven in a determined course.

It is a still further object of the invention to provide a servo means operating on hydraulic or pneumatic principles wherein the power supplied to the steerable wheel is maintained within predetermined limits irrespective of the rate or amount of delivery of the power from the rotating wheel to the fluid circulating system.

It is a still further object of the invention to insure that power may not be applied to the landing wheel for steering purposes until the airplane has landed and the steerable wheel is traveling along the ground, thus insuring against inadvertent manipulation of the steerable wheel prior to landing with consequent danger of ground looping or capsizing of the plane when it is traveling at landing speeds.

Still further objects of the invention will become apparent as the description proceeds.

The invention may take a variety of forms;

7 Claims. (Cl. 244-50) for example, the energy may be taken from the invention together with a part of the movable wheel by means of a gear rotatable therewith and connected to another for'transmission of the energy thereto. may be taken from the wheel through the intermediary of a roller arranged to bear on the tire of the wheel. The energy thus derived may be used either in the mechanical form in which it has been derived or after transformation into hydraulic or any other form.

A convenient arrangement is one in which, as in one of the particular embodiments of the invention hereinafter described, the directional movements of steerable landing wheels are imparted thereto by a servo-motor which is supplied from a source of energy consisting of a hydraulic pump operable by a roller bearing on the tire of the wheel and which includes two piston and cylinder units, the pistons of which tend respectively to move the wheels in opposite directions when liquid supplied by the pump is directed thereto.

In this arrangement, the installation may conveniently comprise a distributing head for the operating fluid of the pump, which is remotely controlled by the pilot, and a feeding tank for.

the pump.

The improved landing gear in accordance with this invention may include means for damping the so-called shimmy oscillations which often are met with in landing gears having steerable landing wheels.

The invention will now be further described in reference to the accompanying drawings, in which:

Figure 1 is a side elevation of a steerable landing wheel constructed in accordance with the supporting frame;

Figure 2 is a top plan view with parts omitted,

and Figure 3 is a part section and part plan taken on the line C-D of Figure 1;

Figure 4 is a diagrammatic lay-out of the fluid connections and associated parts of a steering control system using the steerable landin wheel double wheel and the support therefor illustrated H in Figure 5;

Figure 8 is an enlarged sectional view of the wheel and power take-oil shown in Figure 6;

Alternatively, the energy Figure 9 is a vertical section through a landing wheel in accordance with this invention employing an entirely mechanical construction as hereinafter described; and

Figures 10 and 11 are respectively horizontal sections through Figure 9 on the section lines lll--l and ll-ll of that figure with parts omitted.

Referring to Figure 1 and its subordinate Figures 2 and 3, wheel I iscarried by a fork 2 supported by and depending from the shaft 3. This shaft is guidedin the body of the dash-pot 4 serving as a wheel carrier. The wheel and its accessories are elements of a retractable landing gear of which the retractable frame 5 is shown.

Mounted adjacent the top of the wheel carrier are a pair of hydraulic cylinders 6.

As shown in Figures 1 and 2, a gear segment I is mounted for rotation with a reduced portion 3a of the shaft 3, being rotated therewith by means of a grooved connection as shown in Figure 2 which at the same time permits slide vertically with respect to the segment I in accordance with the adjustments upward and downwardly of shaft 3 within the dash-pot 4 in absorbing shocks transmitted from the wheel in landing and traveling over rough ground. A toothed sector 8 mounted on astub shaft 9 carried in an extension H) of the-housing of the dash-pot 4 is associated in meshing engagement with the segment I.

A lever l l is secured at its midpoint to the shaft 9 and at its opposite endsto rods l2 connected to the operating pistons I3 of the cylinders 6.

' As shown in part in Figures 1 and 3 and in further detail in Figur 4, the cylinders 6 are connected in a liquid circulating systemincluding a hydraulic pump 14, a liquid collecting tank or sump- It, a four-way valve l8, fluid supply pipes 20 extending from the casing 22 of the valve l8 to the respective cylinders, valve controlled by pass connections 2425 between the respective supply pipes 20 and the collecting tank l6, and a secondby-pass connection 26 from the valve casing 22 to the collecting tank that is operable when the valve 18 is in mid or neutral position and it is desired that the steerable wheel shall be maintained in a straight course.

As shown in Figures 1 and 3, the pump I4 is housed within a roller 28 carried by the arms 30 pivoted at 3| on brackets carried by the fork 2 and is driven through suitable connections by the roller when the latter is brought into driving engagement with the periphery of the wheel I. The collecting tank IG'is likewise supported by arms 32 from the fork 2 and is connected with the pump by the pipe connection 33.

As shown in Figure 4, return flow of-iiquid through the connections 24--25 is controlled by valves 34 associated with push rods 38 adapted to reciprocate within the valve chambers 38 and carrying cam followers 40 at their inner. ends.

Springs 3| the shaft 3a toacting between abutments 0n the.

4 44 which is set to permit flow through the pipe 23 in preference to flow through the connections 24-25 when the valve I8 is in its mid or neutral position as shown in Fig. 4.

. The operation of the device may be described as follows: 7

When the airplane is driven along a straight course, the valve l8 and the cam 42 assume the symmetrical positions shown inFigure 4. The pump then delivers liquid through the valve l8 into the tank l6.

The adjustment of the spring'tension on the valve is so arranged that the pressure maintained in the liquid supply connections and the cylinders 6 will insure a correct damping of the shimmy or tendency to sidewise oscillation of the wheel. v

When the pilot wants to produce a turning movement, he causes the simultaneous rotation valves and the push rods urge the cam followers against the periphery of a cam 42 having a low or dwell portion 42a and a high portion or sector 42b. The cam 42 is mounted coaxially with the valve 18 and is movable in coordinated relation therewith under remote control by the pilot. As shown, the cam is mounted within a casing 43 which receives the returning liquid from the connections 24 and discharges it through the connection 25 to the collecting tank. v

Flow through the second return connection 24 is controlled by means of the spring pressed, valve of the valve member 18 and the cam 42. The

liquid discharged from the pump is then admitted to only one of the cylinders 6. The piston l3 of this cylinder is then urged outwardly pivoting the lever II and thestub shaft 9 and through the latter rotating the toothed sector 8 and the segment 1, which latter turns the shaft 30. and the wheel I. Springs, not shown, auto matically return the lever II to mid or neutral position when the wheel is retracted on take-off. The pressure that maybe applied to the pistons through their cylinders when a turning movement is initiated is determined by pre-adjustment of the tension of the springs operating between the push rods and their corresponding valves. It will be understood that if the liquid flow is directed to one cylinder by manipulation of the valve III, the cam, which turns to a corresponding extent, will cause the corresponding cam follower 40 to ride up onto the higher portion 42b of the cam, thus increasing the spring tension and consequent resistance to flow of liquid through the corresponding by-pass connectiton 24 past the valve 34 disposed therein to the return connection 25.

On the other side, the cam being suitably designed, the cam follower 40 travels on the lower or dwell portion 42a of the cam, thus exerting a relatively low spring pressure on the valve 34 as sociated therewith and permitting liquid to flow past its valve from the corresponding cylinder 6 to the return line 25.

In this manner, the force applied to the wheel in turning is controlled as desired and is a function only of the positions of the controlling parts they automatically insure damping or minimiz-,

ing of "shimmy oscillations independently of the damping action that may be obtained by maintained balanced fluid pressures in the opposed hydraulic cylinders as described above. The association of a double wheel construction in a landing gear .of the present invention is particularly desirable when the transmission of the tuming force is effected entirely by mechanical means as shown, for example, in the modification of Figures 9-1 1.

In Figures 5-8 inclusive there is shown a modifled form of the invention wherein the power take-oil. from the rotating double wheel la is effected by means of a transmission chain 50 driven by a sprocket 52 mounted on the shaft 54 which carries the wh'eel la. The transmission chain drives a sprocket 56 mounted on the pump shaft 58. The pumpfla is shown as carried within the lower end of the housing 60 of the wheel support.

As shown more particularly in Figure '7, the pistons I3a of the opposed cylinders 6a are connected on opposite sides of the vertical axis of the wheel support to a sector plate 62 which is connected to and rotatable with the hollow shaft 63 supporting the wheel mounting 6|. ,Liquid supply connections 20 are provided between the pump Ila and the cylinders 6a. Valve controlled by-pass connections, not shown, similar to those shown in Figure 4, are also provided.

Figures 9, 10 and 11 illustrate a further embodiment of the invention wherein the directional control is effected entirely through mechanical means. Power is taken from the shaft 54a by means of the drivin sprockets 52a and 52b and transmission chains 50a and 50b respectively which in turn drive the sprockets 56a and 56b mounted on shafts 66 and 61 carrying worms.68 and 69. The worms 68 and 69 are driving engagement respectively with the worm gears 10 and H mounted on the centrally arranged hollow shafts I2 and 13 which of said valves being adapted when open to prothe cam is operated to shift'the cam followermeans and thereby vary the spring pressure on said valves.

2. Inan aircraft landing gear, the combination of a support secured to the aircraft, a wheel frame pivotally mounted on said support and including a pivot shaft and a landing wheel for the aircraft which is mounted on said shaft, a pair are supported within the swivel mounting I4.

At theiropposite ends the shafts 12 and 13 carry brake pulleys l5 and 16 which respectively engage brake bands TI and'l8. The brake bands are connected for remote control by the pilot by any suitable means, as for example by means of hydraulic spring jacks'IS and 80 as shown in Figures and 10.

The turning angle of the swivel mounting with respect to the support 8| may be limited by suitable stops, not shown.

Although those embodiments of the invention employing a fluid circuit system have been described with particular reference to the use of a liquid as the fluid circulating medium, it will be understood that compressed air or other pneumatic means may be employed. It will also be understood that the above described embodiments of the invention are illustrative only and that the invention may be applied in many other way and take different forms from those illustrated. The invention is not to be deemed as limited, therefore, otherwise than as indicated by the appended claims.

What I claim as my invention and desire to secure by Letters Patent of the United States is:

1. In an aircraft landing gear, the combination of a support secured to the aircraft, a wheel unit swiveling in said support and including a landing wheel for the aircraft, a pair of cylinderpiston units operatively connected in opposed relationship between said support and said wheel frame to exert opposed torques to said wheel frame, means including a pump driven by said landing wheel for supplying fluid to said cylinders, manually controlled valve means to selectively control the supplying of fluid to said cylinders thereby to control the swiveling of said wheel frame, a by-pass cam operatively connected to be operated simultaneously with the operation of said valve means, valve conduit means having valves therein associated respectively with the supply of fluid to each of said cylinders, each of cylinder-piston units mounted in opposed relationship between said wheel frame and said support to exert opposed pivotal torques on said wheel frame, a hydraulic pump operatively connected to said landing wheel to be operated by the rotation of the landing wheel, conduit means connecting said hydraulic pump to said cylinders,

' valve means in said conduit means to control the supplying of liquid to said cylinders, a cam operated simultaneously with the operation of said valve means, and means, operatively connected with said valve means and with said cam whereby the liquid supplied to said cylinders is controlled with the result that the pivoting of the wheel frame is regulated.

3. In an aircraft landing gear, the combination of a support secured to the aircraft, a wheel frame pivotally mounted on said support and including a pivot shaft and a landing wheel for the aircraft, a pair of cylinder-piston units each of which comprises a cylinder and a piston therein, said units being mounted in opposed relationship between said wheel frame and said support to exert opposed pivotal torques on said wheel frame, a fluid pump means operatively connected to said landing wheel to be operated by the rotationthereof, conduit means connecting said pump means to supply fluid under pressure to said cyle inders, valve means in said conduit means to control individually the supplying of fluid to said cylinders whereby the opposed pivotal torques are controlled, a rocking member mounted adjacent said shaft and connected at its end to the respective ends of said cylinder-piston unit the other end .Of each of which is connected to said support, a gear segment rigidly mounted with respect to said rocking member, and gear means mounted on said shaft and meshing with said gear segment whereby rocking movement which is transmitted to said rocking arm by said units is transmitted through said gear segment to said gear means and thence to said shaft.

4'. In an aircraft landing gear having a steerable wheel carried by a wheel supporting unit, a shaft connected to said unit and rotatable to steersaid wheel, steering meansincluding cams secured to said shaft and located on opposite sides of a plane passing through said shaft, cylinders having pistons movable therein and eng n said cams, means driven by said wheel for supplying fluid to said cylinders, and manually operable means controlling the flow of fluid to said cylinders.

5. In an aircraft landing gear in which a support is secured to the aircraft and a landing wheel assembly is mounted on said support for pivotal movements about a vertical axis, in combination, a pair of cylinder-piston units mounted in opposed relation for exerting opposed pivotal 7 torques on said landing wheel assembly in response to fluid pressures applied within said cylinders, a fluid circulating pump driven by a landing wheel forming a part of said assembly, conduits establishing fluid flow connections between said pump and said cylinders, valve means for selectively controlling the supply of fluid to said cylinders and thereby regulating the steering torques exerted by said cylinder-piston 11mm, and means for controlling the turning movements of said assembly including a cam operable simultaneously with said valve means for controllingv the return flow of fluid from said cylinder-piston units to said pump.

6. In an aircraft landing gear in which a support is secured to the aircraft. and a landing wheel assembly is pivoted on said support for swivelling movements in the steering of the aircraft, in combination, a pair of cylinder-piston units each of which is formed by a cylinder and a piston therein, said units being mounted in opsupplied under pressure by said pump to said by regulate the relatlve steering torques exerted by said cylinder-piston units.

'1. In an aircraft landing gear in which a support is secured to the 'aircraftand a' landing wheel assembly is mounted on saidsupp'ort for pivotal movements about a vertical axis. in combination, a pair of cylinder-piston units mounted in opposed relation for exerting v(H M-Rid pivotal torques on said landing wheel assembly in response to fluid pressures applied within said cylinders, a fluid circulating pump driven by a landing wheel forming a part of said assembly, conduits establishing fluid flow connections between said pump and said cylinders, valve means operable to establish fluid flow connections from said pump to said cylinders i'electively or simultaneously as desired. and means operable when said valve is positioned to permit fluid flow to,

both of said cylinders, for resiliently urging said wheel into alignment with the axis of the aircraft, said means including a conduit establishing a fluid flow by-pass between said valve and said pump and a pressure relief valve controlling fluid flow through said by-pass.

PIERRE ERNEST MERCER. 

